How Volcanoes Froze the Earth (Twice) (S03E22)

S03E01 When Humans Were Prey S03E02 How Blood Evolved (Many Times) S03E03 The Humans That Lived Before Us S03E04 The Island of Shrinking Mammoths S03E05 The Evolution of the Heart (A Love Story) S03E06 How 7,000 Years of Epic Floods Changed the World S03E07 The Island of Huge Hamsters and Giant Owls S03E08 The Giant Bird That Got Lost in Time S03E09 When We First Made Tools S03E10 When Giant Scorpions Swarmed the Seas S03E11 When We Tamed Fire S03E12 The Mystery Behind the Biggest Bears of All Time S03E13 The Croc That Ran on Hooves S03E14 When We Took Over the World S03E15 The Ghostly Origins of the Big Cats S03E16 The History of Climate Cycles (and the Woolly Rhino) Explained S03E17 The Hellacious Lives of the "Hell Pigs" S03E18 How Evolution Works (And How We Figured It Out) S03E19 When the Synapsids Struck Back S03E20 When Ichthyosaurs Led a Revolution in the Seas S03E21 When We Met Other Human Species S03E22 How Volcanoes Froze the Earth (Twice) S03E23 How Earth's First, Unkillable Animals Saved the World S03E24 When Giant Deer Roamed Eurasia S03E25 Was This Dinosaur a Cannibal? S03E26 The Missing Link That Wasn’t S03E27 The Raptor That Made Us Rethink Dinosaurs S03E28 When Bats Took Flight S03E29 How Pterosaurs Got Their Wings S03E30 When Giant Lemurs Ruled Madagascar S03E31 When Antarctica Was Green S03E32 The Case of the Dinosaur Egg Thief S03E33 When Hobbits Were Real S03E34 Were These Monsters Inspired by Fossils? S03E35 How We Domesticated Cats (Twice) S03E36 When Giant Hypercarnivores Prowled Africa S03E37 Why Male Mammoths Lost the Game S03E38 The Forgotten Story of the Beardogs S03E39 The Fuzzy Origins of the Giant Panda